The bloody battery in the transit keeps draining over 4 days.......to nothing.

Now i have checked that everything is off and that no internal lights are staying on but it still happens

ALSO

It can go for 4 days and start.....then i will give it a 5 minute drive to makle sure it is ok. The next day go to start it and nothing.

It does this with the 3 different batteries i have so i wouldnt say it is the battery.

Any ideas?????